1. Field of the Invention
The present invention generally relates to a novel process for the synthesis of olefinic silanes and/or siloxanes. More particularly, the process provides the dehydrocondensation of a silicon-containing compound with an olefin in the presence of a rhodium or ruthenium catalyst in a one-step process.
2. Prior Art
The hydrosilation reaction was discovered in 1947 and over the years has become one of the best known and most widely practiced reactions in organosilicon chemistry, including its use in a wide variety of large scale commercial applications. It has also been the subject of several extensive reviews, see for instance: Organic Insertion Reactions of Group II Elements, Consultants Bureau, NY, 1966; Organometallic Compounds of the Group IV Elements, Deckker, NY, 1968, Vol. I; Preparation of Carbofunctional Organosilanes By An Addition Reaction, Moscow, 1971; Russ. Chem. Rev. 46, 264 (1977); and J. Organometal. Chem. Library 5, 1977, pg 1-179.
The hydrosilation reaction between a silane and an olefin is generally depicted as follows: ##STR1##
In operating a hydrosilation reaction, various transition metals are known to be effective catalysts. U.S. Pat. No. 2,823,218 teaches chloroplatinic acid, a soluble form of platinum, as a particularly effective hydrosilation catalyst.
The literature has also disclosed dehydrocondensation (also known as dehydrogenative silylation) between silanes and olefins. This reaction is depicted as follows: ##STR2##
In U.S. Pat. No. 3,595,733 osmium compounds, such as chloroosmic acid, was taught as being capable of catalyzing this dehydrocondensation reaction. However, osmium compounds are very expensive and thus other routes have been explored, such as in British Pat. No. 1,365,431 where nickel complexes are disclosed as catalyzing the reaction of .tbd.SiH compounds with olefins to provide organosilicon compounds having olefinic unsaturation.
More recently, rhodium and ruthenium have been suggested as a possible dehydrocondensation catalyst.
In JP No. 57,140,788 2-(perfluorohydrocarbyl) vinyl silanes were prepared by the reaction of .tbd.SiH with perfluorohydrocarbyl--containing olefins in the presence of rhodium or ruthenium catalyst complexes.
It has been suggested in the literature that triethylsilane undergoes a dehydrocondensation reaction instead of hydrosilation with olefins such as styrene of 1-decene using RhCl(PPh.sub.3).sub.3 or Ru.sub.3 (OH).sub.12 as a catalyst, J. Org. Chem. 1984, 49, 3389-3392.
Ru.sub.3 (CO).sub.12 was reported to catalyze a dehydrocondensation reaction between simple silanes and olefins in Angew. Chem. Int. Ed. Engl. 19 (1980) 928.
Rhodium catalysts were unexpectedly found to yield E-hex-1-en-1-yl(triethyl)silane and E-hex-2-en-1-yl(triethyl)silane when triethylsilane and hex-1-ene were reacted together in Journal of Molecular Catalysis, 26 (1984) 89-104.
The reaction of simple silanes, including triethoxysilane, with an olefin in the presence of a rhodium catalyst was found to generate .beta.-silyl-substituted trans-styrenes. In this reaction, excess styrene was employed and selectivity was reportedly enhanced by placing bulky substituents on the silanes. J. Organomet. Chem. 1983, 48, 5101-5105.
Finally, ruthenium phosphine complexes were reported to generate trace amounts of unsaturated product when the reactants were alkoxysilanes and olefins. J. Organomet. Chem., 253 (1983) 349-362.
Although these references generally teach the dehydrocondensation between simple silanes and olefins in the presence of a rhodium or ruthenium catalyst, it is unexpected that this reaction would take place with the more complex secondary aminosilanes, siloxanes, alkoxysilanes and alkylalkoxysilanes.